Late-onset Alzheimer's disease (LOAD) is a multifactorial disease characterised by neurofibrillary tangles and amyloid plaques and can only be definitely diagnosed post-mortem. The disease can begin many years before it is eventually diagnosed. In the early stages, short-term memory loss is the most common symptom. Later, symptoms include confusion, anger, mood swings, language breakdown, long-term memory loss, and the general decline of senses and bodily functions.
Alzheimer's disease (AD) is usually diagnosed clinically from the patient history, observations of relatives, and clinical observations. However, the presence of Alzheimer's disease-characteristic neurological and neuropsychological features such as amyloid plaques and neurofibrillary tangles can often only be determined post-mortem.
Most cases of Alzheimer's disease do not exhibit familial inheritance, however at least 80% of sporadic Alzheimer's cases involve genetic risk factors. Inheritance of the ε4 allele of the apolipoprotein E (ApoE) gene is regarded as a risk factor for development in up to 50% of late-onset sporadic Alzheimer's cases.
Diagnostic markers for neurological disorders are especially important in diagnosis early in the course of disease, when therapeutic compounds have the greatest potential effect. However, accurate diagnosis is difficult. Few diagnostic markers for early stage neuronal disorders are available and those that are available rely on the analysis of sample material (e.g. cerebrospinal fluid), which is difficult and painful to obtain. The use of protein biomarkers in diagnostic medicine is increasing. Identification of protein biomarkers of Alzheimer's disease, especially those present in readily accessible biological fluids such as blood and urine, represents a desirable and effective alternative to current diagnostic methods.
WO2011/067610 describes a method for aiding the diagnosis of Alzheimer's disease comprising determining the level of expression of at least four platelet proteins in a patient sample, wherein the number of alleles of ApoE4 determines the identity of the at least four platelet proteins selected.
However, there is a need to develop further diagnostic methods using peripheral biomarkers of Alzheimer's disease which enable simpler and more accurate diagnosis of disease.